a) Field of the Invention
The present invention relates to a lithographic printing plate capable of performing in a press without using any wetting liquid.
B) Description of the Prior Art
Hitherto the practically used conventional lithographic printing plates comprise forming oil-sensitive areas and non oil-sensitive areas on substantially the same surface of a substrate such as a zinc plate, an aluminum plate and so forth. When performing the press operation using such prior art printing plates, there can be obtained final printed materials by applying a wetting liquid to non-image areas (non oil-sensitive areas) and applying an oily ink selectively to image areas (oleophilic oil-sensitive areas) and then transferring said oily ink to printing papers through a blanket.
It is well known that the aforesaid printing methods, in which a wetting liquid is used, have encountered various kinds of troubles. In order to eliminate disadvantages resulting from the use of a wetting liquid, therefore, a series of studies and investigations have hitherto been carried out by plate material traders, printers and others. For instance, Japanese Patent Publication No. 29722/1973 discloses a printing plate comprising an ink-repellent layer made of a silicone rubber, an oil-sensitive layer and a substrate, Japanese Laid Open Patent Application No. 904/1975 discloses a printing plate which comprises embedding in an ink-repellent layer particle image patterns that constitute an ink receiving portion, and Japanese Laid Open Patent Application No. 119705/1974 shows a printing plate which comprises provision of a low adhesive layer and a high adhesive layer on a substrate. However, these presently proposed lithographic printing plates are disadvantageous in that plate-making consumes a considerably long time, care is needed in treating plate materials, distinct and ground-unstained printing materials are in fact not obtainable, and further said printing plates are inferior in printing durability.